1. Field of the Invention
The present invention relates to apparatus for loosening or removing the skins from products such as nut kernels, beans, seeds or the like.
2. Related Art
Various devices employing different techniques are known for removing the skins from such products.
With particular reference to nut kernels, devices are known which scrub, brush or scrape the nut kernels, or use other abrasive type treatments to remove the nut kernel skins. In certain cases, 40% of the treated products still have their skins adhered thereto. It is then necessary electro-optically or manually to sort the products and re-treat those on which the skins remain.
In most cases, prior to employing the above skin removing processes, the nuts are pre-treated to loosen the skins for their more efficient removal. Typically pre-treatment involves soaking the nut kernels in water or a suitable aqueous solution. Alternatively the pre-treatment may take the form of roasting the kernels or heating them in hot air, steam, water or an aqueous solution.
The speed and efficiency at which nuts can be processed in these known methods of skinning is reduced by the additional pre-treatment process steps involved. Although necessary in order to attain skinned nuts of the required quality, these pre-treatment steps may thus be undesirable since they add time to the skinning operation as a whole. The apparatus required for such pre-treatments moreover usually involve considerable extra plant investment costs and maintenance costs.
Particular forms of pre-treatment also have their particular associated problems. For example, with treatments that involve a nut kernel being heated, the heat so applied can cause damage to the kernel""s cell structure, reducing its shelf life and affecting its flavour characteristics. Also, when heating the nut kernel has only been partially successful in loosening the kernel skin, repeating is not desirable due to the likelihood of damage.
Soaking forms of pre-treatment have the disadvantage that they are typically highly time consuming. In one known process for example, nut kernels are soaked in water or sodium hydroxide for about eight hours. Since all the nut kernels have to pass through the soaking step before they are skinned, the output of the skinning process will depend on the amount of nuts which can be soaked at any given time. Soaking in chemical solutions requires careful monitoring in order to ensure that the nut kernels are themselves not damaged by the action of the solution.
It has been proposed in U.S. Pat. No. 4,537,122 to skin almond nuts by fluidising a bed of nuts with air. In this system, the nuts are first presoaked and washed to remove 90-95% of their skins and the remaining 5-10% is removed by the fluidising air. Thus several steps are involved.
It has been proposed in U.S. Pat. No. 4,300,447 to skin peanuts by the abrasive action of a rotating cylinder in combination with jets of air. Again, in this proposal, it is preferred for the raw peanuts to be preconditioned by warm or hot air or hot water or aqueous solution. A significant proportion of the nuts may remain unskinned without such pre-treatment.
It has been proposed in U.S. Pat. No. 2,651,345 to provide a machine which uses water jets as part of a process to remove the skins from hazelnuts. The nuts are contained in a series of parallel elongate chambers where they are supported on rotating rolls having spiral ridges for conveying the nuts along the chambers whilst being subjected to jets of water discharged from fixed nozzles. The rolls form a moving floor of each chamber and the jets are angled to strike the nuts with xe2x80x9cglancing blowsxe2x80x9d when the nuts are positioned centrally at the lowermost region of the chamber, between the rolls. In order to be sure that there are no nuts above a correctly positioned nut, which would shield that nut from the jets, each nut must effectively be conveyed individually along a chamber during the skinning process and this is inefficient in terms of production rates. The machine is complicated in that the rotating rolls have to be provided and in that the jets of water have to be carefully aimed to provide the desired glancing blows. In addition, the rotation of the nuts on the rolls demands, in the main, uniformly spherical and uniformly sized nuts, thereby limiting the types and varieties which can be used in the machine. For example, certain types of hazelnut are xe2x80x9cacornxe2x80x9d or xe2x80x9cconexe2x80x9d shaped and will not readily turn on the rolls.
A similar rotating roll conveyance system for nuts has been proposed in U.S. Pat. No. 3,077,217. Thus, in this proposal there are also fixed nozzles directing a spray into an elongate chamber having a floor formed by a pair of adjacent rotating rolls, the nuts being conveyed substantially individually along the chamber by a helical groove on one of the rolls. The other roll has an abrasive surface for removing the nut skins, assisted by a hot water spray (140xc2x0 F. to 175xc2x0 F.) at a pressure of 40 psi to 80 psi. Because of the need to abrade the nuts at the floor of the chamber, the nuts have to be conveyed individually along the chamber and there are again limitations in production rates and the ability to deal with products of different shape and size.
It has been proposed in U.S. Pat. No. 4,738,860 to provide a machine concerned exclusively with walnuts. The walnuts are subjected to water jets, at a preferred pressure ranging from 30 psi to 100 psi, but this does not itself remove the skins. During spraying the walnuts are contained in cup shaped containment areas formed by a fine mesh fabric net or screen. Although the document suggests that the walnuts can move freely within the containment area during spraying, there will be a tendency, if more than one layer of walnuts are put in the containment area, for there to be a xe2x80x9cdeadxe2x80x9d region at the bottom of the cup-shape where walnuts will remain and thus not be exposed directly to the spray. It will therefore be generally necessary to load the containment area with only one layer of walnuts and this will again impose a limitation on production rates.
Further concerning U.S. Pat. No. 4,738,860, following the application of water jets, the skinned walnuts and the skins are taken together to a centrifuge and thereafter the skins and the nut meat are separated by means of an air blower. The process therefore requires an additional step to remove the skins from the skinned nuts.
According to the present invention there is provided apparatus for removing the skin from products such as nut kernels, beans, seeds or the like, comprising receiving means arranged to receive a plurality of the products in a body thereof with the products in contact with each other, the receiving means having liquid outlet means, and liquid discharge means adapted to direct a jet or jets of liquid at the products so as to remove their skins, whereby the skins removed from the products are carried away from the skinned products by said liquid and via said outlet means of the receiving means.
The action of the jet or jets of liquid loosens and removes the skins whilst in addition creating movement of the products which allows the skins to escape. The liquid serves to carry away the removed skins. The combination of the liquid action and abrasion between the products provides a very efficient process in which the skins of a large number of products may be simultaneously removed from the skinned products and carried away therefrom. The time taken to remove the skins is relatively short, for example of the order of 90 seconds for Oregon hazelnuts and of 35 seconds for Turkish hazelnuts.
Preferably, the products are not pre-treated before being subjected to the jet or jets of liquid. Thus for example raw products, such as hazelnut kernels, may be subjected to the jet or jets of liquid. This saves expense and time in the production process, and preheating or presoaking, and the use of chemicals or even water in a pre-treatment step or steps, can be avoided. However, there are some products which benefit from pre-treatment. For example, almonds can be scalded for a short period of time (such as 10 seconds) and then subjected to the jet or jets of liquid. This is a considerable reduction from the usual two minute scalding time applied to almonds to loosen their skins prior to removal by pinch rollers. There is therefore an improvement in the efficiency of the process in that a reduced pre-treatment time is involved. Moreover, there will be less moisture increase during the combined scalding and skinning steps than during the usual more lengthy scalding step, leading to a shorter or cooler drying step and thus savings in time and energy and maintenance of oil, flavour and colour characteristics of the products.
In the preferred embodiments, the liquid used is water, a readily and cheaply available product.
The or each jet may be produced by discharging the liquid through a liquid discharge means, such as a nozzle. The nozzle is preferably such as to produce a so-called flat-spray jet. This is a jet which diverges from the nozzle at an angle and in cross-section (perpendicular to the flow direction) has the shape of an ellipse with the major axis considerably greater than the minor axis. The divergence angle may be very small, thereby concentrating the effect of the jet over a small area, but increased coverage is obtained with a wider jet which is able to impact against a larger number of products simultaneously. Thus the nozzles may be such as to produce a flat-spray jet with spray angles of, for example, 15xc2x0, 25xc2x0, 40xc2x0, 65xc2x0, 80xc2x0, 95xc2x0 or 110xc2x0. Suitable nozzles are supplied by Lurmark Limited, of Longstanton, Cambridge, England and a particularly effective nozzle made by that company is model B2CM02E15, which produces a 15xc2x0 flat-spray jet.
The required pressure of the liquid will depend on the products to be skinned and the shape of the jet or jets. The liquid may be pressurised at a pressure in the range of 35 psi (pounds per square inch) to 600 psi, although high pressures, up to 2000 psi or even 5000 psi may be appropriate for some products. Preferred pressure ranges are 80 psi to 600 psi, 150 psi to 600 psi, 200 psi to 600 psi, 250 psi to 600 psi, 300 psi to 600 psi, 350 psi to 600 psi, and 400 psi to 600 psi. Other preferred ranges are 200 psi to 500 psi, more preferably 300 psi to 500 psi. In a preferred process involving the skinning of hazelnut kernels, a pressure of 450 psi to 500 psi, e.g. 475 psi, has proved very effective.
Lower pressures may be effective with a narrow spray angle (since spray impact is greater with narrower spray angles at a similar flow rate) and/or with the jet being generated by discharge means in close proximity to the products, whilst higher pressures may be required with a wide spray angle and/or with the jet being generated further away from the products.
The pressurisation of the liquid will normally be generated by a pressure source such as a pump. Reciprocating pumps are preferred, although other pumps may also be used. Where several jet discharge means are used, the pressure source will need to be of sufficient capacity to maintain an adequate pressure supply to all the discharge means. It may be desirable to use more than one pressure source.
Liquid flow rates will vary depending on the pressures used and the size of the nozzle. Flow rates may vary for example in a range of 5 to 12 liters per minute per nozzle.
For some products, heat may be used if it is beneficial, but in view of the effectiveness of the process heat is not generally necessary. Preferably, therefore, no heat is used in the process; in other words, the liquid used is at ambient temperature. This saves on energy costs. Moreover, the cell structure of the product is unchanged, thereby making it possible to return for reprocessing any products with skin still adhering to their surface. However, in view of the efficiency of the skin removal process, it will generally be necessary to repeat the method on only a small proportion of the products, if any.
It is desirable that over a period of time all the products in the receiving means are exposed directly to the jet or jets of liquid. Preferably, therefore, the receiving means is configured such that in response to liquid jetting, products disposed in a lowermost region of the body of products are caused to move to an upper region of the body of products, in which upper region they are exposed directly to the jet or jets of liquid. Such an arrangement is of independent patentable significance, both in the context of a system for removing product skins and a system for loosening them prior to final removal by other known means, e.g. pinch rollers.
Viewed from a further aspect, therefore, the invention provides a process of loosening or removing the skin from products such as nut kernels, beans, seeds or the like, the process comprising receiving in receiving means a plurality of products in a body thereof, subjecting the products to a jet or jets of liquid directed at the body of products from above so as to loosen or remove the skins of the products, and causing, by the configuration of the receiving means and in response to the liquid jetting, products disposed in a lowermost region of the body of products to move to an upper region of the body of products, in which upper region they are exposed directly to the jet or jets of liquid.
Viewed from another aspect the invention provides apparatus for loosening or removing the skin from products such as nut kernels, beans, seeds or the like, the apparatus comprising receiving means for receiving a plurality of products in a body thereof, and liquid discharge means for directing a jet or jets of liquid at the body of products from above so as to loosen or remove their skins, wherein the receiving means is configured such that, in response to liquid jetting, products disposed in a lowermost region of the body of products are caused to move to an upper region of the body of products, in which upper region they are exposed directly to the jet or jets of liquid.
Viewed from another aspect the invention provides a receiving means for receiving a plurality of products such as nut kernels, beans, seeds or the like, the receiving means being adapted to receive the plurality of products in a body thereof and to have a jet or jets of liquid directed at the body of products from above so as to loosen or remove the skins of the products, the receiving means being configured such that, in response to liquid jetting, products disposed in a lowermost region of the body of products are caused to move to an upper region of the body of products, in which upper region they are exposed directly to the jet or jets of liquid.
The configuration of the receiving means thus causes any products disposed in the lowermost region of the body thereof, where they may not be adequately exposed to the jet or jets of liquid, to move to an upper region where they are exposed directly to the jet or jets. This can ensure efficient skin loosening or removal, even with the products in a body comprising more than one layer of products. A relatively large quantity of products can thus be processed for a given area covered by the jet or jets of liquid.
Products in the upper region will generally fall under gravity to a lower position and then be recycled back to the upper region. A tumbling process can be achieved in which each individual product is repeatedly exposed to the jet or jets. This will tend to result in a different part of each product being presented to the jet or jets on each exposure, whereby substantially all surfaces of the products in the receiving means are exposed over a period of time.
In a preferred arrangement, the configuration of a stationary portion, e.g. a floor, of the receiving means can be such as to achieve the desired product movement. This is beneficial as compared to rotating rolls which require a drive mechanism and may cause undesirable excessive abrasion of the products.
The receiving means preferably has a plurality of upwardly sloping portions to cause or promote upward movement of the products. Such upwardly sloping portions, which may for example be in the form of ridges or ramps, can assist both in helping the products to move upwardly from the lowermost region and in achieving the tumbling motion of the products which is desirable for their various surfaces to be exposed to liquid jetting.
It is desirable to impart lateral movement to the products. If there are upwardly sloping portions, lateral movement of the products will bring them into contact with the upwardly sloping portions and hence cause the products to move upwardly. Thus, in use of a preferred embodiment, a given product will follow a generally lateral path as viewed in plan, and will move up and down as it moves along this path. Each upward movement will be caused by a respective upwardly sloping portion, and the product will then tend to drop down again. Preferably, the lateral movement of the products is along a path in the form of an endless loop. The process can therefore continue for as long as is desired whilst maintaining continuous movement of the products.
The lateral path of movement of the products can be achieved by providing the jet or jets with a horizontal component. Another way of causing or aiding lateral product movement is to provide the receiving means with a plurality of channel portions which slope downwardly in a direction to cause liquid to flow in that direction. Such a flow can act on the products and promote their lateral movement in the direction of liquid flow. Each channel portion is preferably defined by two adjacent ridges which form upwardly sloping portions.
The process may be operated such that substantially no liquid is retained in the receiving means.
Preferably, however, the process comprises retaining an amount of liquid in the receiving means, for example up to one third of the height of the receiving means, and causing the retained liquid to flow laterally in the receiving means. This flow will assist lateral movement of the products. It can be caused by a horizontal component of the jet or jets, and/or by sloping channel portions feeding liquid into the body of retained liquid. Maintenance of a certain amount of liquid in the receiving means may be effected by appropriate sizing of liquid outlet means having regard to the rate of liquid input from the jet or jets.
If the upwardly sloping portions are in the form of a plurality of ridges, these may be arranged generally parallel to each other in a row. Preferably, however, they extend outwardly from a central region. Over a period of time, a product will move round the central region and return to its starting point.
The receiving means will in general be configured such that there are no xe2x80x9cdeadxe2x80x9d regions where the products can rest without movement. In a preferred embodiment the receiving means has a central region blocked off to prevent the products from going there. This will be particularly advantageous if the area covered by the jet or jets is generally ring-shaped or annular, because the products will not be able to go to the center of the ring.
With certain products, such as almonds, the skins may in some circumstances be loosened but not entirely removed by the liquid jet-or jets. With other products, such as hazelnuts, the skins are removed. Preferably, therefore the liquid outlet means are large enough for skins removed from the products to be carried away from the skinned products by the liquid, but small enough not to allow escape of the skinned products. A plurality of round holes or elongate slots may be provided. An advantage of an elongate slot is that removed skins tend to be xe2x80x9cleafxe2x80x9d shaped and can thus be carried by a flow of liquid through a relatively narrow slot.
The receiving means is preferably made of a substantially smooth material, to minimise abrasion between the receiving means and the products which could lead to lost weight and pitting. The rough effect created by the wires of a mesh material is thus less preferred for many products. A preferred material is polycarbonate, although other materials are of course suitable.
The liquid discharge means may be fixed above the receiving means. It may then be desired to move the receiving means to achieve relative movement between it and the liquid discharge means. Preferably, however, the receiving means is stationary during liquid jetting and the position of the liquid discharge means of the jet or jets is moved. The liquid discharge means is preferably coupled to a driving mechanism, although in some circumstances such a mechanism is not required if the liquid discharge means is arranged so as to be movable relative to the receiving means in response to the reaction force generated by the liquid discharged. In a preferred embodiment, a driving mechanism, e.g. an electric motor, is provided to drive the liquid discharge means and is assisted by the reaction force of the liquid discharged.
In a preferred embodiment the liquid discharge means is provided vertically above the products and the movement occurs in a horizontal plane. Providing the jet or jets vertically above the products makes the process easier to carry out, as the products can simply be disposed in an open-topped container and retained therein by gravity, with the jets being directed at the products through the open top of the container.
In a particularly preferred embodiment, the liquid discharge means is rotatably movable. The rotatable arrangement of the discharge means can be achieved in various ways. Preferably, the liquid discharge means comprises a pair of nozzles, each nozzle being attached to one of the two ends of a rotatable support, the support being disposed above the receiving means, and the support being arranged to rotate above the receiving means.
Providing two nozzles at the ends of a rotatable support allows the forces exerted on the nozzles by the jets of liquid being discharged therefrom to be balanced, so that there is little or no resultant force on the support or its mounting. The forces will however form a couple tending to make the bar rotate.
Further, providing two nozzles means that there are two jets of liquid impacting on the products rather than just one, which results in an increased frequency of impact and hence a reduced processing time.
The direction in which the liquid discharge means is oriented may be vertical or near vertical. It is preferred that the direction of discharge of each nozzle is between 0xc2x0 and 20xc2x0 to the vertical, e.g. 9xc2x0.
Although the discussion above has referred to receiving means and liquid discharge means in the singular, it will be appreciated that a plurality of receiving means can be provided, each one having e.g. a pair of nozzles disposed above it, to increase the amount of product that can be processed at any one time.
The spacing of the jet discharge means from the body of the products may be chosen according to the particular products, the pressure used, the spray-angle etc. A spacing not greater than 6 inches is preferred, and a spacing in the range of 1-3 inches is particularly preferred.
Preferably the spacing between the discharge means of the jet or jets of liquid and the body of products is adjustable. This may be advantageous if the same apparatus is to be used for different products.
It is possible to load the receiving means with products at a product loading station where skin loosening or removal is also carried out, either by arranging the jet discharge means to be permanently located at the loading station or to be movable to the loading station after loading. It is however preferred for the receiving means to be movable from a product loading station to a skin loosening or removal station. Unloading of the processed products may also be carried out at the same station as loading and processing, but again it is preferred for the receiving means to be movable from the skin loosening or removal station to a product unloading station.
Movement of the receiving means between the stations may for example be effected by sliding or rolling of the receiving means on tracks, rails or the like. Return of the receiving means after unloading to the loading station may be effected manually or by appropriate conveying means. For example, the receiving means may be mounted on a chain conveyor, whereby the receiving means follows a forward, upwardly facing path and a return, downwardly facing path.
Loading of the receiving means may be carried out manually or by known hopper and product dosing arrangements. Unloading may be carried out manually or by known tipping mechanisms, suitably adapted if necessary. If a chain conveyor as mentioned above is used, tipping is effected automatically.
The receiving means advantageously encloses the products to prevent them from escaping during skin removal, whilst of course permitting the removed skins to be carried away. The receiving means may therefore have a lid which is closed after loading. Preferably, the receiving means is open-topped at the product loading station and a lid for the receiving means is provided at the skin removal station. This is particularly convenient, since in a process involving several receiving means only one lid needs to be provided. The lid will of course be such as to allow entry of the jet or jets to the receiving means.
Following skin removal, the products can be dried. This can be carried out for example using known dehumidification equipment. It will generally be desirable to dry the products at air temperatures below about 45xc2x0 C., preferably about 40xc2x0 C., so as to avoid heating of the products which would tend to reduce their shelf life.